Cornheads are harvesting heads mounted on the front of agricultural harvesting machines, like combines or forage harvesters. During operation, cornheads pull down adjacent rows of corn plants and snap the ears of corn of the plants. The cornheads comprise a number of row units arranged side by side, each of which having a pair of stalk rolls (or one stalk roll interacting with a rigid wall) for pulling the plants down. Above the stalk rolls, stripper plates are mounted, forming a forwardly extending stripper gap, through which the plant is pulled down by the stalk rolls. The distance between the stripper plates is generally adjustable and selected such that the stalk can pass, while the ears are removed from the stalks by the stripper plates and fed by a conveyor, usually a chain conveyor, to a cross auger feeding the ears to the interior of the harvesting machine.
In the prior art, laterally movable stripper plates biased towards another stripper plate by means of a spring with adjustable force have been described, allowing the stripper gap to automatically adjust to the diameter of the plant stalks:
IT 1 291 063 A shows a cornhead row unit with laterally shiftable stripper plates that are coupled at their outer lateral edges by respective pivot links to vertically extending levers. One lever is provided at the front and one at the rear end of the stripper plates. The levers are, beneath the stripper plates, fixed to a forwardly extending shaft connecting both levers. The shaft rotates around its longitudinal horizontal, forward axis.
The rear lever extends down beneath the shaft and is connected to a horizontal helical spring biasing the lever to the outside. This force is transmitted by the lever and the shaft to the stripper plate, which is thus biased towards the other stripper plate. The position of the lever with respect to the spring can be adjusted by a screw thread in order to adjust the spring force. This arrangement is relatively complex and further has the disadvantage that, due the geometry of the mechanism, binding of the stripper plates can occur.
DE 100 12 088 A1 shows another cornhead with spring-biased stripper plates. Helical pressure springs extend in the plane of the stripper plates between the laterally shiftable stripper plates and fixing members at the outer edges of the row unit frame. An adjustment of the spring bias is not provided.
What is needed, therefore, is a cornhead row unit with a stripper plate that is spring-biased by a reliable and uncomplex mechanism. It is an object of this invention to provide such a device in the independent claims of the present application. Further advantages are provided by each of the dependent claims.